Black spots on Mint Leaves (5+ Causes & How to Fix them?)

Imagine spending hours planting mint leaves, and discovering black spots forming on them. It’s disheartening, isn’t it? I certainly felt that way. However, I was determined not to give up. I delved into various methods to fix the issue, and fortunately, I succeeded in saving my mint plant leaves.

If you’re experiencing the same problem, you’ve come to the right place. Here, you’ll find the solution to save your mint leaves from black spots. What are you waiting for, let’s save the mint plant as soon as possible.

In this guide, I’ve provided a clear explanation of the causes behind the black spots on mint leaves, along with their symptoms and treatment. This will make it easy for you to identify why your mint leaves are affected. If you encounter any more issues in the future, feel free to ask me in the comment section.

Quick takeaways:

• Mint is the plant that adds such a cool flavor to dishes and drinks. Most of the gardens have it.
• There can be various causes that the mint leaves are getting blackish-colored spots which sometimes look brown-colored as well.
• The summer days never go without taking out the mint leaves and eating them to feel refreshed.
•  Some of them are Pest infestation, mint rust, mint leaf blight, and many more explained below.

What are the causes behind the black spots on mint leaves?

As mentioned there are various causes behind the black spots on mint leaves. So, have a look at them so that you come to know about the preventive measures. They are as follows:

1. Mint rust
2. Mint leaf blight
3. Verticillium wilt
4. Anthracnose
5. Pests

So, let’s know about these causes and also treatments in more detail:

Mint rust

Many times when the mint leaves start to have brown spots, it comes out they have mint rust. Mint rust is a fungal infection caused by Puccinia methane, which is mostly seen in mint plants during the onset of the summer season or the end of springtime.

The mint leaves have a powdery layer at the back and start with the powdery spots which are very small in size, in a shade of orange or yellow color. The plant starts to look weird with brown spots. 

Symptoms

• Start with yellow dusty spots and with turn black colored.
• The plant looks dull and spots appear on the shoot portion as well.
• Shedding of leaves occurs with time as the plant gets super weak.

Treatment

• Keep the plant clean
• Don’t let the leaves stay wet for long. However, you shouldn’t wet the mint leaves that much.
• The old dead parts should be removed from plants as well as soil which can lead to fungal growth
• If the spots have just started, you need to dig the plant up, give heat treatment at 111 degrees Fahrenheit for 10-11 minutes to kill the attacks, and then transfer to the cold water for a similar time duration and then replant it. If the plant is too infected it is better to destroy the plant or dump it away from the garden as it can harm other plants too. 
• Use clean, sterilized tools for gardening purposes
• You can use fungicides to kill fungi that have azoxystrobin, tebuconazole, and myclobutanil in them.

Mint leaf blight

Mint leaf blight is actually mint rust more harshly. The mint leaf blight caused by fungus leads to black spots on the mint leaves.

The fungus Cephalosporium leads to mint leaf blight in the mint plants. The moist conditions and water splashes lead to this disease.

The mint mostly gets this issue during the winter or spring season when it is too rainy or humid. The disease can be transferred to other mint plants through cutting or close contact with healthy ones

Symptoms

• The leaves and as well stems get affected.
• The lower leaves are affected by the odd-shaped black spots.
• The parts get weak and also fall off.

Treatment

• The diseased mint rhizomes need to be removed or destroyed.
• Don’t wet the leaves for a long time. Keep leaves dry.
• The overhead watering should be avoided
• Again give them heat treatment, you can also use specialized chemicals designed to get rid of mint leaf blight.

Verticillium wilt

The verticillium wilt is caused by the fungus that lives in soil and is named verticillium dahlia. This fungus also leads to black spots on mint leaves.

They spread through spores and get active in the wet conditions of spring and summertime. The roots are the first target as the fungus is soil-borne and then the lower leaves get affected. 

Symptoms

• As the name indicates, wilting of plants is a common symptom where the plant doesn’t get enough water as the root system is damaged.
• The growth gets stunted, and spots start to be visible on the stem also
• The leaves curl and twist and they drop from the plant prematurely. 

Treatment

• Use sanitized tools and sterilized growing medium
• Don’t let weeds grow, remove them as quickly as possible
• Give the plant warm dry conditions, and cut the affected parts if the infection has just started.

Anthracnose

This disease also causes black spots on the leaves of the mint plant. The lower side of the leaves is usually affected. In rare cases, the new parts are also seen affected. The difference is that the black spots expand with time and lead to the blackening of the whole leaf. 

Symptoms

• Leaves twist, black spots on stems, and leaves occur
• Whole leaves turn black
• Stunted growth of plant’

Treatment

• Prune the diseased parts of the plants.
• Avoid overhead irrigation.
• Mulch the soil and sanitize the tools.

Pests

Below are the pests that tend to cause brown spots on the mint leaves as follows:

Aphids

The black spots are caused by aphids that might cause fungal diseases in such a situation. Aphids like peach aphids are the main agents for causing black spots.

The plants get stunted, with dusty spots on the leaves. Just remove the diseased parts from the plants, and clean the leaves with insecticidal soap or neem oil. 

Cutworms

The cutworms harm the plants by cutting them at the base, making them weak with dead spots on the leaves. Making use of insecticide spray, pick the cutworms, and throw them far away.

Thrips

Last but not least, Thrips attack also can cause black spots on the leaves of mint plants. The leaves might die due to full infection.

Leaves drop after some time. Wash them with a strong water jet, use sticky traps to collect them, and use insecticidal sprays.

Useful tips for Mint Leaves

Some of the tips for preventing black spots on mint leaves are as follows:

• One thing that you can do is to provide the proper amount of water to the plan so that they remain moist and well-draining.
• A good flow of air will let the plant grow well. If you provide them with poor air circulation, then it will create fungus in the plant.
• Make sure you are pruning your plant on time so that the shape and size of the plant remain maintained.
• Do not overcrowd plants by planting them with each other.
• You can do some research and plant the other varieties of mint that are disease-resistant.
• Last, but not least, you have to rotate your crop with time which will reduce the attack of diseases in the plant. 

Is it safe to have mint leaves that have turned black?

It is better that you avoid eating the mint leaves with black spots. The black color on the green leaves is an indication of something unhealthy. So, the consumption of brown spots on Mint leaves will harm your health if you eat it continuously.

The feeling of eating such black mint leaves is also not good. Eating healthy green leaves is always a better and healthy option. 

Summing up the context

The mint leaves are yummy and have healthy ingredients in the food. We understand how it feels if mint leaves are showing brown colors and fewer green leaves.

Though we have uploaded the main causes that lead to black spots on the leaves, there are some other causes like too much sunlight, not enough sunlight, overwatering, underwatering, rootbound mint plants, and too much fertilizer that also cause such issues. I hope I helped you out with your worry and made your mint plant healthy.

Happy planting and minting!